ARM: Support inlined version of %_FastAsciiArrayJoin on ARM

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
===================================================================
--- src/arm/full-codegen-arm.cc	(revision 6989)
+++ src/arm/full-codegen-arm.cc	(working copy)
@@ -3200,9 +3200,236 @@
 
 
 void FullCodeGenerator::EmitFastAsciiArrayJoin(ZoneList<Expression*>* args) {
+  Label bailout, done, one_char_separator, long_separator,
+      non_trivial_array, not_size_one_array, loop,
+      empty_separator_loop, one_char_separator_loop,
+      one_char_separator_loop_entry, long_separator_loop;
+
+  ASSERT(args->length() == 2);
+  // We will leave the separator on the stack until the end of the function.

[William Hesse, 2011/03/01 13:54:11]

This comment seems inconsistent with the "pop separator" line below.

[Søren Thygesen Gjesse, 2011/03/01 14:08:31]

Done.

+  VisitForStackValue(args->at(1));
+  // Load this to r0 (= array)
+  VisitForAccumulatorValue(args->at(0));
+
+  // All aliases of the same register have disjoint lifetimes.
+  Register array = r0;
+  Register elements = no_reg;  // Will be r0.
+  Register result = no_reg;  // Will be r0.
+  Register separator = r1;
+  Register array_length = r2;
+  Register result_pos = no_reg;  // Will be r2
+  Register string_length = r3;
+  Register string = r4;
+  Register element = r5;
+  Register elements_end = r6;
+  Register scratch1 = r7;
+  Register scratch2 = r9;
+
+  // Separator operand is on the stack.
+  __ pop(separator);
+
+  // Check that the array is a JSArray.
+  __ JumpIfSmi(array, &bailout);
+  __ CompareObjectType(array, scratch1, scratch2, JS_ARRAY_TYPE);
+  __ b(ne, &bailout);
+
+  // Check that the array has fast elements.
+  __ ldrb(scratch2, FieldMemOperand(scratch1, Map::kBitField2Offset));
+  __ tst(scratch2, Operand(1 << Map::kHasFastElements));
+  __ b(eq, &bailout);
+
+  // If the array has length zero, return the empty string.
+  __ ldr(array_length, FieldMemOperand(array, JSArray::kLengthOffset));
+  __ SmiUntag(array_length, SetCC);
+  __ b(ne, &non_trivial_array);
+  __ LoadRoot(r0, Heap::kEmptyStringRootIndex);
+  __ b(&done);
+
+  __ bind(&non_trivial_array);
+
+  // Get the FixedArray containing array's elements.
+  elements = array;
+  __ ldr(elements, FieldMemOperand(array, JSArray::kElementsOffset));
+  array = no_reg;  // End of array's live range.
+
+  // Check that all array elements are sequential ASCII strings, and
+  // accumulate the sum of their lengths, as a smi-encoded value.
+  __ mov(string_length, Operand(0));
+  __ add(element,
+         elements, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
+  __ add(elements_end, element, Operand(array_length, LSL, kPointerSizeLog2));
+  // Loop condition: while (element < elements_end).
+  // Live values in registers:
+  //   elements: Fixed array of strings.
+  //   array_length: Length of the fixed array of strings (not smi)
+  //   separator: Separator string
+  //   string_length: Accumulated sum of string lengths (smi).
+  //   element: Current array element.
+  //   elements_end: Array end.
+  if (FLAG_debug_code) {
+    __ cmp(array_length, Operand(0));
+    __ Assert(gt, "No empty arrays here in EmitFastAsciiArrayJoin");
+  }
+  __ bind(&loop);
+  __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
+  __ JumpIfSmi(string, &bailout);
+  __ ldr(scratch1, FieldMemOperand(string, HeapObject::kMapOffset));
+  __ ldrb(scratch1, FieldMemOperand(scratch1, Map::kInstanceTypeOffset));
+  __ JumpIfInstanceTypeIsNotSequentialAscii(scratch1, scratch2, &bailout);
+  __ ldr(scratch1, FieldMemOperand(string, SeqAsciiString::kLengthOffset));
+  __ add(string_length, string_length, Operand(scratch1));
+  __ b(vs, &bailout);
+  __ cmp(element, elements_end);
+  __ b(lt, &loop);
+
+  // If array_length is 1, return elements[0], a string.
+  __ cmp(array_length, Operand(1));
+  __ b(ne, &not_size_one_array);
+  __ ldr(r0, FieldMemOperand(elements, FixedArray::kHeaderSize));
+  __ b(&done);
+
+  __ bind(&not_size_one_array);
+
+  // Live values in registers:
+  //   separator: Separator string
+  //   array_length: Length of the array.
+  //   string_length: Sum of string lengths (smi).
+  //   elements: FixedArray of strings.
+
+  // Check that the separator is a flat ASCII string.
+  __ JumpIfSmi(separator, &bailout);
+  __ ldr(scratch1, FieldMemOperand(separator, HeapObject::kMapOffset));
+  __ ldrb(scratch1, FieldMemOperand(scratch1, Map::kInstanceTypeOffset));
+  __ JumpIfInstanceTypeIsNotSequentialAscii(scratch1, scratch2, &bailout);
+
+  // Add (separator length times array_length) - separator length to the
+  // string_length to get the length of the result string. array_length is not
+  // smi but the other values are, so the result is a smi
+  __ ldr(scratch1, FieldMemOperand(separator, SeqAsciiString::kLengthOffset));
+  __ sub(string_length, string_length, Operand(scratch1));
+  __ smull(scratch2, ip, array_length, scratch1);
+  // Check for smi overflow. No overflow if higher 33 bits of 64-bit result are
+  // zero.
+  __ cmp(ip, Operand(0));
+  __ b(ne, &bailout);
+  __ tst(scratch2, Operand(0x80000000));
+  __ b(ne, &bailout);
+  __ add(string_length, string_length, Operand(scratch2));
+  __ b(vs, &bailout);
+  __ SmiUntag(string_length);
+
+  // Get first element in the array to free up the elements register to be used
+  // for the result.
+  __ add(element,
+         elements, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
+  result = elements;  // End of live range for elements.
+  elements = no_reg;
+  // Live values in registers:

[William Hesse, 2011/03/01 13:54:11]

array_length must be live here, because you use it below.

[Søren Thygesen Gjesse, 2011/03/01 14:08:31]

Done.

+  //   element: First array element
+  //   separator: Separator string
+  //   string_length: Length of result string (not smi)
+  __ AllocateAsciiString(result,
+                         string_length,
+                         scratch1,
+                         scratch2,
+                         elements_end,
+                         &bailout);
+  // Prepare for looping. Set up elements_end to end of the array. Set
+  // result_pos to the position of the result where to write the first
+  // character.
+  __ add(elements_end, element, Operand(array_length, LSL, kPointerSizeLog2));
+  result_pos = array_length;  // End of live range for array_length.
+  array_length = no_reg;
+  __ add(result_pos,
+         result,
+         Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
+
+  // Check the length of the separator.
+  __ ldr(scratch1, FieldMemOperand(separator, SeqAsciiString::kLengthOffset));
+  __ cmp(scratch1, Operand(Smi::FromInt(1)));
+  __ b(eq, &one_char_separator);
+  __ b(gt, &long_separator);
+
+  // Empty separator case
+  __ bind(&empty_separator_loop);
+  // Live values in registers:
+  //   result_pos: the position to which we are currently copying characters.
+  //   element: Current array element.
+  //   elements_end: Array end.
+
+  // Copy next array element to the result.
+  __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
+  __ ldr(string_length, FieldMemOperand(string, String::kLengthOffset));
+  __ SmiUntag(string_length);
+  __ add(string, string, Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
+  __ CopyBytes(string, result_pos, string_length, scratch1);
+  __ cmp(element, elements_end);
+  __ b(lt, &empty_separator_loop);  // End while (element < elements_end).
+  ASSERT(result.is(r0));
+  __ b(&done);
+
+  // One-character separator case
+  __ bind(&one_char_separator);
+  // Replace separator with its ascii character value.
+  __ ldrb(separator, FieldMemOperand(separator, SeqAsciiString::kHeaderSize));
+  // Jump into the loop after the code that copies the separator, so the first
+  // element is not preceded by a separator
+  __ jmp(&one_char_separator_loop_entry);
+
+  __ bind(&one_char_separator_loop);
+  // Live values in registers:
+  //   result_pos: the position to which we are currently copying characters.
+  //   element: Current array element.
+  //   elements_end: Array end.
+  //   separator: Single separator ascii char (in lower byte).
+
+  // Copy the separator character to the result.
+  __ strb(separator, MemOperand(result_pos, 1, PostIndex));
+
+  // Copy next array element to the result.
+  __ bind(&one_char_separator_loop_entry);
+  __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
+  __ ldr(string_length, FieldMemOperand(string, String::kLengthOffset));
+  __ SmiUntag(string_length);
+  __ add(string, string, Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
+  __ CopyBytes(string, result_pos, string_length, scratch1);
+  __ cmp(element, elements_end);
+  __ b(lt, &one_char_separator_loop);  // End while (element < elements_end).
+  ASSERT(result.is(r0));
+  __ b(&done);
+
+  // Long separator case (separator is more than one character). Entry is at the
+  // labe long_separator below.

[William Hesse, 2011/03/01 13:54:11]

label

[Søren Thygesen Gjesse, 2011/03/01 14:08:31]

Done.

+  __ bind(&long_separator_loop);
+  // Live values in registers:
+  //   result_pos: the position to which we are currently copying characters.
+  //   element: Current array element.
+  //   elements_end: Array end.
+  //   separator: Separator string.
+
+  // Copy the separator to the result.
+  __ ldr(string_length, FieldMemOperand(separator, String::kLengthOffset));
+  __ SmiUntag(string_length);
+  __ add(string,
+         separator,
+         Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
+  __ CopyBytes(string, result_pos, string_length, scratch1);
+
+  __ bind(&long_separator);
+  __ ldr(string, MemOperand(element, kPointerSize, PostIndex));
+  __ ldr(string_length, FieldMemOperand(string, String::kLengthOffset));
+  __ SmiUntag(string_length);
+  __ add(string, string, Operand(SeqAsciiString::kHeaderSize - kHeapObjectTag));
+  __ CopyBytes(string, result_pos, string_length, scratch1);
+  __ cmp(element, elements_end);
+  __ b(lt, &long_separator_loop);  // End while (element < elements_end).
+  ASSERT(result.is(r0));
+  __ b(&done);
+
+  __ bind(&bailout);
   __ LoadRoot(r0, Heap::kUndefinedValueRootIndex);
+  __ bind(&done);
   context()->Plug(r0);
-  return;
 }